JP2003018409A - Image processor and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit and image processing method that can reproduce characters or the like formed on a background area with sharpness without causing white Bordering or a turbid color. SOLUTION: An MTF correction section 21 is provided with a replacement control section 113. The replacement control section 113 comprises two AND circuits 114, 115 and a replacement filter section 116. The AND circuit 114 receives an in-solid character area signal (- BETA- MOJI) and a NOT logic signal of a character area detecting in-edge signal (- INEDGE), and the AND circuit 115 receives an in-dot character area signal (- AMI- MOJI) and the NOT logic signal of the character area detecting in-edge signal (- INEDGE). The replacement filter section 116 receives output signals from the AND circuits 114, 115. Then the replacement filter section 116 replaces the lightness of a target pixel into the average lightness of the background area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and an image processing program for correcting image data in order to sharply reproduce characters and the like. More specifically, characters on a halftone dot area or a solid area having a predetermined density (hereinafter collectively referred to as “base area”) are sharply reproduced without causing white edging or color turbidity. The present invention relates to an image processing device and an image processing program that can be performed.

[0002]

2. Description of the Related Art An image is read using a CCD sensor,
In a digital copying machine or the like that decomposes into pixels and performs image processing, edge enhancement processing is performed in order to sharply reproduce characters and fine lines. In this edge enhancement processing, the density of the inner part of the edge (hereinafter referred to as “inner edge”) is made higher, and the outer part of the edge (hereinafter referred to as “outer edge”)
Is a process for lowering the concentration of. By such processing, the edge area becomes clear, and characters and fine lines are sharply reproduced.

However, when the edge enhancement processing is performed on a character or the like formed on the background area, there is a problem that a white border is formed around the character as shown in FIG. Therefore, measures have been taken to solve such problems. As one of the countermeasure technology,
For example, there is one disclosed in Japanese Patent Laid-Open No. 2000-307869. With this technology, when edge enhancement processing is performed on halftone dots, etc., the edge enhancement processing is not performed on the outer edge area to prevent white edging from being formed around the characters. ing.

[0004]

However, in the technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 2000-307869, the sharpness of the characters formed on the halftone dots is lowered,
There was a problem that color turbidity occurred. This is because the edge enhancement processing is not applied to the outer edge area, and thus the smoothing processing is applied to this area similarly to the halftone dot area. As a result, the characters on the halftone dots are blurred, and color turbidity occurs, so that a high-quality reproduced image cannot be obtained. The same can be said for characters and the like formed on a solid area having a predetermined density.

Therefore, the present invention has been made to solve the above-mentioned problems, and it is possible to clearly reproduce characters and the like formed on the base region without causing white edging or color turbidity. An object of the present invention is to provide an image processing apparatus and an image processing program that can be performed.

[0006]

SUMMARY OF THE INVENTION An image processing apparatus according to the present invention, which has been made to solve the above problems, provides an image data acquisition unit for acquiring image data and an image data acquired by the image data acquisition unit. Based on the outer edge discriminating means for discriminating whether or not the target pixel belongs to the outer edge region which is the outer portion of the edge region, and whether or not the target pixel belongs to the base region based on the image data acquired by the image data acquiring unit A background area determining unit that detects a background area by determining, and a first correction unit that performs a first correction process on a pixel of interest that is determined to belong to the outer edge area by the outer edge determining unit; A second correction unit that performs a second correction process different from the first correction process on the pixel of interest that is determined to belong to the outer edge region by the edge determination unit, and the outer edge determination unit It is determined that the first correction process is performed by the first correction unit on the target pixel that is determined not to belong to the base region by the base region determination unit among the target pixels that are determined to belong to the target region. However, for the pixel of interest determined to belong to the background region by the background region determination means, the second
Correction processing determining means for determining that the second correction processing is performed by the correcting means. The "base area" here includes a halftone area as well as a solid area having a predetermined density.

In this image processing apparatus, first, image data is acquired by the image data acquisition means. Here, the image data acquisition means may read the image itself to acquire the image data, or may acquire the image data obtained by reading the image with a scanner or the like. Furthermore, the image data may be acquired from a recording medium into which the image data is input, a network, or the like. That is, the image data acquisition means may be a scanner or the like, a data reading device, an input port, a modem or the like, and includes all devices capable of acquiring image data.

In this way, when the image data is acquired by the image data acquiring means, the outer edge discriminating means determines whether or not the pixel of interest belongs to the outer edge area which is the outer portion of the edge area based on the image data. Is determined. Further, the background area determination means determines whether or not the pixel of interest belongs to the background area based on the image data acquired by the image data acquisition means. Then, the base region is detected from the determination result. That is, the distribution area of the pixels determined to belong to the base area is detected as the base area. Note that the above-mentioned determination of each area may be performed by a known method. Further, the outer edge discriminating means may discriminate the outer edge region by detecting the inner edge region.

Then, the first correction processing by the first correction means or the first correction processing by the second correction means for the pixel of interest determined by the outer edge determination means to belong to the outer edge region A different second correction process is performed.
Here, whether to perform the first correction processing or the second correction processing is determined by the correction processing determination means. That is, among the target pixels determined to belong to the outer edge area by the outer edge determination means by the correction processing determination means, the target pixel determined to not belong to the base area by the base area determination means First by the first correction means
It is determined that the correction processing of is performed. On the other hand, among the target pixels determined to belong to the outer edge area, the target pixel determined to belong to the base area by the base area determination unit is determined to be subjected to the second correction processing by the second correction unit. To be done.

Here, the edge correction processing is performed as the first correction processing by the first correction means, and the replacement processing for replacing the density of the pixel of interest with the peripheral density is performed as the second correction processing by the second correction means. I'll do it. The ambient concentration is
It is a typical density (for example, average density) of pixels in a predetermined area adjacent to the pixel of interest. By doing so, the edge attenuation processing is performed on the pixel of interest (such as a normal character formed on the paper) that is determined to belong to the outer edge area but not to the base area. It should be noted that the inner edge region may be edge-emphasized as usual. Therefore, by such image processing, the edge portion of the character or the like becomes clearer, and the character or the like can be sharply reproduced. In addition, since there is no base, white borders are not formed around characters.

On the other hand, the replacement process is performed on the target pixel (such as a character formed on the background) which is determined to belong to both the outer edge area and the background area. In this replacement process, the density of the pixel of interest is replaced with the density of its surroundings. As a result, the density of the image in the outer edge area on the base area becomes equal to the density of the peripheral image. Therefore,
No white borders around letters or fine lines on the background. Further, since such a pixel of interest is not subjected to the smoothing process, the sharpness of the reproduced characters and thin lines on the background is not lowered, and the color turbidity is not generated.

In particular, it is desirable that the replacement process be a process of replacing the average density in the area detected as the background area by the background area determination means. As a result, it is possible to reliably prevent the situation where the density of the boundary part of the characters drawn on the background, that is, the density in the outer edge area becomes almost the same as the density of the background, and a white border is formed around the characters. Because you can In addition, "concentration" here
In addition to the density value, the value includes a value having a correlation with the density (for example, brightness).

Here, as the average density, an average value of the densities of the pixels determined to belong to the base area within a predetermined matrix centered on the pixel of interest (for example, about 5 × 5 size) may be used. Therefore, when a character area is included in the predetermined matrix, the average density calculated by excluding the area is used. Further, the matrix size may be set according to the state of the background on which characters and the like are drawn. For example, if the background is halftone dots,
The size may be set to such a degree that the influence of white isolated points forming halftone dots can be ignored. Also, when the density of the background is changing, the matrix size should not be made too large. This is to prevent the replaced density from being significantly different from the density of the adjacent base.

Further, the image processing apparatus according to the present invention has an image data acquisition means for acquiring image data, and an outer edge area in which the pixel of interest is an outer part of the edge area based on the image data acquired by the image data acquisition means. Edge determining unit that determines whether the pixel of interest belongs to the background region by determining whether the pixel of interest belongs to the background region based on the image data acquired by the image data acquiring unit. And the density of the target pixel which is determined to belong to the outer edge area by the outer edge determining means and which belongs to the base area by the base area determining means is calculated based on the densities of the peripheral pixels of the target pixel. And a replacement means for replacing the value with the specified value.

Also in this image processing apparatus, first, image data is acquired by the image data acquisition means. Then,
The outer edge discriminating unit discriminates whether or not the pixel of interest belongs to the outer edge region which is the outer portion of the edge region, based on the image data acquired by the image data acquiring unit.
Further, the background area determination means determines whether or not the pixel of interest belongs to the background area based on the image data acquired by the image data acquisition means. Then, the base region is detected from the determination result.

Then, the density of the pixel of interest determined by the replacing means to belong to the outer edge area by the outer edge determining means and to belong to the background area by the background area determining means is the density of the pixel of interest. It is replaced with a value calculated based on the density in the peripheral pixels. Therefore, a white border does not occur in the outer edge area on the background area, that is, around the characters on the background. Further, since such a pixel of interest is not subjected to smoothing processing,
The sharpness of the reproduced characters and fine lines on the background does not decrease, and color turbidity does not occur.

Here, it is preferable that the replacing means uses the average density in the area detected as the background area by the background area determining means as the value calculated based on the density in the peripheral pixels of the target pixel. As a result, the density of the boundary portion of the characters drawn on the background, that is, the density of the outer edge region becomes substantially equal to the density of the background, and a higher quality reproduced image can be obtained. The method for calculating the average concentration is
The above method may be used.

Here, the above-mentioned image area discriminating apparatus is not limited to the case of being configured by hardware, but can be realized by processing by software. Therefore,
As shown below, it may exist as an image processing program.

That is, as an example, the image processing program according to the present invention causes a computer to perform an image data acquisition step of acquiring image data, and a pixel of interest outside the edge region based on the image data acquired in the image data acquisition step. The outer edge determination step for determining whether or not it belongs to the outer edge area which is a part, and the background area by determining whether or not the pixel of interest belongs to the background area based on the image data acquired in the image data acquisition step. Among the target pixels determined to belong to the outer edge area in the base area determination step and the outer edge determination step, the target pixel determined to belong to the base area in the background area determination step is focused on. Replace the pixel density with the average density in the area detected as the background area in the background area determination step. A correction processing step of performing a replacement process is intended to run.

With these image processing programs, it is possible to operate the computer, that is, the software is read into the computer, and the computer and the software cooperate to realize the above-described image processing apparatus. Then, it is possible to obtain the same effect as that of the image processing apparatus described above.

Among the target pixels determined to belong to the outer edge area in the outer edge determination step in the correction processing step, the target pixels determined to not belong to the base area in the base area determination step Edge attenuation processing may be performed. This is because characters formed in the non-base area, that is, characters formed on a normal paper surface are reproduced very clearly.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The most preferred embodiment of the present invention will be described below in detail with reference to the drawings.
FIG. 1 shows a schematic configuration of the color image processing apparatus according to this embodiment. Such a color image processing device can be applied to a digital copying machine, a printer, a facsimile, and the like.

The color image processing apparatus according to this embodiment includes a CCD sensor 11, an image synthesizing section 12, an A / D converting section 13, a shading correcting section 14, and a line interval for performing correction between lines. The correction unit 15, the chromatic aberration correction unit 16 that corrects the chromatic aberration of each color, and the magnification / movement processing unit 17
A color conversion unit 18, a color correction unit 19, and a region determination unit 20.
The MTF correction unit 21 and the printer I / F 22 are provided.

The CCD sensor 11 receives reflected light obtained by scanning an original with a scanner and photoelectrically converts it to obtain an analog RGB signal. The image composition unit 12 is an analog RG acquired by the CCD sensor 11.
Odd component and eve for each B signal
n (even number) components are combined. The A / D conversion unit 13 uses the analog RGB images synthesized by the image synthesis unit 12.
The signal is converted into a digital signal. The image synthesizing unit 12 and the A / D converting unit 13 are provided corresponding to the R, G, and B signals of the RGB signal.

The shading correction unit 14 removes unevenness of the light amount on the image in the main scanning direction. Specifically, before the operation of reading the original, the CCD sensor 11 receives the reflected light from the white plate for shading correction, converts the analog data obtained there into digital data, and then stores the digital data in a memory. Remember. And
When reading a document, the read data of the document is corrected using the digital data stored in the memory as a reference value.

The scaling / move processing unit 17 performs image enlarging / reducing processing and image moving processing by controlling the writing and reading operations of the memory. The color conversion unit 18 performs conversion into a standardized color system, and here, Lab data is created based on RGB signals. Then, the color conversion unit 1
The Lab data created in 8 is input to the color correction unit 19 and the area determination unit 20. The color correction unit 19 creates a recording density signal CMYK capable of recording in a desired color in consideration of the spectral characteristics of the four color toners actually used and the recording process based on the Lab data.

The area discriminating unit 20 discriminates the image attribute for each pixel, generates signals corresponding to the respective attributes, and finally the MTF correcting unit 21 based on these signals.
To generate control signals (CMPX, KMPX). As shown in FIG. 2, the area discrimination unit 20 includes a color signal creation unit 30 and various signal creation units 31.
A halftone dot / color area signal creation unit 32, a halftone dot / solid area character area signal creation unit 33, and an MTF control signal creation unit 34. The various signal creating section 31 includes an edge signal creating section 25 and a solid area signal creating section 26, and a line memory 27 is attached.

Here, the color signal creating section 30 uses the Lab data created by the color converting section 18 to generate a color signal (COLOR) and a black area signal (_BLACK).
Is to create. Then, the color signal creation unit 30
3, as shown in FIG. 3, the conversion unit 35, the color determination threshold table 36, and the black determination threshold table 37.
And two comparators 38 and 39.

The conversion unit 35 uses the data (a7-0, b7-0) created by the color conversion unit 18 and uses the conversion formula (√ (a
² + b ²⁾⁾ by is to create a saturation data (W7-0). The color determination threshold value table 36 creates threshold values for generating a color signal (COLOR) based on the lightness data (L7-0). The black determination threshold value table 37 is for creating a threshold value for generating a black area signal (_BLACK) based on the brightness data (L7-0). Here, the threshold value for generating the color signal (COLOR) and the black region signal (_BLACK) is created based on the brightness data (L7-0) because the saturation amount depends non-linearly on the brightness. This is because

With such a configuration, the color signal generating section 3
In the case of 0, the comparator 38 compares the lightness data (W7-0) with the threshold value created by the color determination threshold value table 36 to create a color signal (COLOR). In the comparator 39, the saturation data (W7-0) and the black determination threshold table 3
The black area signal (_BLACK) is created by comparing with the threshold value created by 7.

Returning to FIG. 2, the various signal generating section 31 determines the isolated point signals (WAMI, KAMI) for halftone dot discrimination and the solid area signal (_BET) based on the brightness data (L7-0).
A), a character area detection edge signal (_EDGL), a character area detection inner edge signal (_INEDG), and a character edge area signal (_EDG). The various signal creating unit 31 includes an edge signal creating unit 25 and a solid region signal creating unit 26 to create these signals.

The edge signal generating section 25 includes an isolated point signal for dot discrimination (WAMI, KAMI), an edge signal for character area detection (_EDGL), an internal edge signal for character area detection (_
INEDG), and character edge area signal (_EDG)
To create. Therefore, as shown in FIG.
1, a feature amount extraction filter unit 42, and two selectors 4
3, 44, four comparators 45 to 48, an outer / inner edge determination unit 49, and two OR circuits 50 and 51.

The matrix creating section 41 creates matrix data of 5 × 5 size from the input image data. Then, the matrix data created by the matrix creation unit 41 is subjected to the filtering process by the feature quantity extraction filter unit 42. Here, the feature amount extraction filter unit 42 includes first-order differential filters (main scanning direction and sub-scanning direction) 52 and 53, second-order differential filters (+ type and x type) 54 and 55, and outer / inner edges. A discrimination filter 56 and an isolated point detection filter 57 are provided.
In the present embodiment, the one shown in FIG. 5 is used as the main scanning direction first-order differential filter 52, and the one shown in FIG. 6 is used as the sub-scanning direction first-order differential filter. Further, the + type second-order differential filter shown in FIG. 7 is used, and the x-type second order differential filter shown in FIG. 8 is used. Further, as the outer / inner edge discrimination filter 56, as shown in FIG.
I am using the one shown in.

Further, the isolated point detection filter 57 shown in FIG.
The one shown in 0 is used. The isolated point detection filter 57 includes a white isolated point detection filter 57a and a black isolated point detection filter 57b. Then, by the white isolated point detection filter 57a, the brightness value of the target pixel V33 is changed to
When the brightness value of the surrounding 8 pixels is larger than the brightness value of the average of 2 pixels in 8 directions, the isolated dot signal (WAMI) for halftone dot discrimination is made "H" active.

That is, when the lightness value of the target pixel V33 satisfies the following condition, it is determined that the target pixel V33 is a white isolated point (WAMI = "H").
The conditions are V33> MAX (V22, V23, V24, V32, V34, V42, V43, V44) and V33> (V11 + V22) / 2 + OFFSET and V33> (V13 + V23) / 2 + OFFSET and V33> (V15 + V24) / 2 + OFFSET and V33> (V31 + V32) / 2 + OFFSET and V33> (V35 + V34) / 2 + OFFSET and V33> (V51 + V42) / 2 + OFFSET and V33> (V53 + V43) / 2 + OFFSET and V33> (V55 + V44) / 2 + OFFSET.

Further, by the black isolated point detection filter 57b, when the brightness value of the target pixel V33 is smaller than the brightness values of the surrounding 8 pixels and smaller than the average brightness value of 2 pixels in 8 directions, the halftone dot discrimination is performed. For isolated point signal (KAMI) "
H "is made active.

That is, when the brightness value of the target pixel V33 satisfies the following condition, it is determined that the target pixel V33 is a black isolated point (KAMI = “H”).
The conditions are V33 <MIN (V22, V23, V24, V32, V34, V42, V43, V44) and V33 + OFFSET <(V11 + V22) / 2 and V33 + OFFSET <(V13 + V23) / 2 and V33 + OFFSET < (V15 + V24) / 2 and V33 + OFFSET <(V31 + V32) / 2 and V33 + OFFSET <(V35 + V34) / 2 and V33 + OFFSET <(V51 + V42) / 2 and V33 + OFFSET <(V53 + V43) / 2 and V33 + OFFSET <(V55 + V44) / 2. OFFSET is a threshold for discriminating isolated points.

Returning to FIG. 4, the output from the primary scanning direction first derivative filter 52 is input to the terminal A of the selector 43, and the output from the sub scanning direction first derivative filter 53 is input to the terminal B of the selector 43. It has been entered. The output from the + -type second derivative filter 54 is input to the terminal A of the selector 44, and the output from the x-type second derivative filter 55 is input to the terminal B of the selector 44. Then, each of the selectors 43 and 44 is adapted to select and output the larger input value to the terminals A and B.

The selector 4 is connected to the terminal P of the comparator 45.
The output (EDG07-00) from 3 is input to the terminal Q of the comparator 45 at the edge reference value (EDGREF
07-00) has been input. Similarly, the output (EDG07-0) from the selector 43 is applied to the terminal P of the comparator 46.
0) is input, and the edge reference value (EDGREF17-10) is input to the terminal Q of the comparator 46. On the other hand, the output (EDG17-10) from the selector 44 is input to the terminal P of the comparator 47, and the edge reference value (EDGREF27-2) is input to the terminal Q of the comparator 47.
0) has been entered. Similarly, the output (EDG17-10) from the selector 44 is input to the terminal P of the comparator 48, and the edge reference value (EDGREF37-30) is input to the terminal Q of the comparator 48.

The output of the comparator 45 and the output of the comparator 47 are input to the OR circuit 50. Further, the output of the comparator 46 and the output of the comparator 48 are input to the OR circuit 51. With the above-described configuration, in the OR circuit 50, the character edge area signal (_EDG) becomes "L" active when either of the following conditions (1) and (2) is satisfied. There is. The conditions are (1)
When the maximum value of the values filtered by the primary scanning direction primary filter 52 and the secondary scanning direction primary filter 53 is larger than the edge reference value (EDGREF07-00), (2) + type secondary differential filter 54 and x The maximum value of the values filtered by the second-order differential filter 55 is the edge reference value (EDGREF27-2
0).

Similarly, in the OR circuit 51, when either of the following conditions (3) and (4) is satisfied, the character area detection edge signal (_EDGL) becomes "L" active. ing. The conditions are (3) primary scanning direction primary filter 52 and secondary scanning direction primary filter 53.
When the maximum value of the values filtered by is larger than the edge reference value (EDGREF17-10), the maximum value of the values filtered by the (4) + type second derivative filter 54 and the x type second derivative filter 55. Is larger than the edge reference value (EDGREF37-30).

To the outer / inner edge judging section 49, the value subjected to the filter processing by the outer / inner edge judging filter 56 and the judgment reference value (INOUT7-0) are inputted. Then, in the outer / inner edge determination unit 49,
The outer / inner edge is determined as shown in FIG. That is, when INOUT7 = 0, the edge detection amount is a positive value (FL238 = 0) and the threshold value (INO
If it is larger than UT6-0), it is determined to be an inner edge. In addition, the edge detection amount is a positive value (FL238 =
0) and smaller than the threshold value (INOUT6-0), or the edge detection amount is a negative value (FL238 = 1).
If it is, it is determined to be an outer edge. On the other hand, IN
When OUT7 = 1, the edge detection amount is a positive value (FL
238 = 0), or the edge detection amount is a negative value (FL238 = 1) and the threshold (INOUT6−
When it is smaller than 0), it is determined as an inner edge. Also,
When the edge detection amount is a negative value (FL238 = 1) and is larger than the threshold value (INOUT6-0), it is determined to be an outer edge. Then, the outer / inner edge determination unit 49
When it is determined that the determination target is the inner edge, the inner edge signal for character area detection (_INEDG) is made "L" active. The threshold (INOUT6
−0) and the edge detection amount (FL237-230) indicate absolute values.

Returning to FIG. 2 again, the solid area signal generating section 2
6 creates a solid area signal (_BETA). In other words, a solid area having a predetermined density is detected. Specifically, FIG.
The solid area signal (_
BETA) is created. That is, first, it is determined whether or not the lightness (L) of the pixel of interest is equal to or lower than the predetermined lightness (th) (# 1). When the brightness of the target pixel is equal to or lower than the predetermined brightness (th), in other words, when the brightness is equal to or higher than the predetermined density (# 1: YES), first, the number of consecutive pixels of the same brightness adjacent to the left side of the target pixel. nl is counted, and the counted value is temporarily stored in the line memory 27 (#
2). The "pixels having the same brightness" may include pixels having the same brightness as the pixel of interest, and pixels having a brightness within a predetermined range (within ± several gradations) with respect to the brightness of the pixel of interest.

Similarly, the number nr of pixels of the same brightness on the right side of the target pixel and the number n of pixels of the same brightness on the upper side of the target pixel.
u, the number nd of pixels having the same lightness below the target pixel is temporarily stored in the line memory 27 (# 3, # 4, # 5).
Then, the continuous same-brightness pixel numbers nm and ns in the main scanning direction and the sub-scanning direction are calculated by the following equations, and the calculation result is temporarily stored in the line memory 27 (# 6).

Nm = nr + nl + 1 ns = nu + nd + 1

Next, it is determined whether or not both the numbers of consecutive pixels of the same brightness nm, ns, are larger than a threshold value (thresh). It should be noted that the threshold may be set to a value that does not discriminate an area having an area forming a character image of a normal size from a solid area having the same brightness according to the recording pixel density. Then, when both the numbers of consecutive same-brightness pixels nm and ns are larger than the threshold value (# 7: YES), it is determined that the pixel of interest belongs to the solid area of the same brightness, and the solid area signal (_
BETA) is activated (# 8). On the other hand, if at least one of the numbers of consecutive same-brightness pixels nm and ns is smaller than the threshold value (# 7: NO), it is determined that the pixel of interest does not belong to the same-brightness solid area, and the solid-area signal (_BETA). Is not activated (# 9). Further, in # 1, even when the brightness of the pixel of interest is equal to or higher than the predetermined brightness (# 1: NO), it is determined that the pixel of interest does not belong to a solid area having the same brightness (# 9). After that, the above-described processing is sequentially performed on each pixel to detect a solid area having the same lightness.

Returning to FIG. 2, the halftone-dot / color-area-signal creating section 32 determines the color area signal (_COL_DOT) based on the color signal (COLOR) and the halftone dot discriminating isolated point signal (WAMI, KAMI). And a halftone dot area signal (_AMI). That is, halftone dot /
The color area signal creation unit 32 determines a halftone dot area and a color area. Then, in the area discrimination unit 20, the dot / color area signal creation unit 32 causes the color area signal (_COL_DOT) and the dot area signal (_AM).
Pixels for which both the signals I and I are activated are determined to belong to the color halftone dot area. As shown in FIG. 13, the halftone dot / color area signal creating unit 32 includes a black isolated point number counting unit 60, a white isolated point number counting unit 61, a color pixel number counting unit 62, and an adder 6.
Three, four comparators 64-67 and an OR circuit 68 are included.

The black isolated point number counting unit 60 is 9 × 45.
The number of black isolated points existing in the matrix area is counted. Similarly, the white isolated point number counting unit 61
The number of white isolated points existing in the 9 × 45 matrix area is counted. The output from the black isolated point number counting section 60 is output to the terminal A of the adder 63 and the comparator 6.
5 is input to each terminal P. On the other hand, the output from the white isolated point number counting section 61 is the terminal B of the adder 63.
And to the terminal P of the comparator 66.
The output from the adder 63 is input to the terminal P of the comparator 64. Here, each reference value (CNTREF17-10, CNTREF17-10,
27-20, 37-30) are input respectively.
The outputs from the comparators 64 to 66 are OR circuits 68.
Has been entered in.

Accordingly, in the OR circuit 68, when the total value of the number of black isolated points and the number of white isolated points is larger than the reference value (CNTREF17-10), the number of black isolated points is the reference value (CNTREF27-20). )
If the number of white isolated points is greater than the reference value (CNTREF37-30) and at least one of the conditions is satisfied, it is determined that the pixel of interest belongs to the halftone dot area, Area signal (_AMI)
Is made "L" active.

Further, the color pixel number counting section 62 is 9 ×
The number of color pixels existing in the 45 matrix area is counted. Then, the output from the color pixel number counting unit 62 is input to the terminal P of the comparator 67. Here, the reference value (CNT
REF47-40) has been input. As a result, in the comparator 67, the number of color pixels is changed to the reference value (C
NTREF47-40), it is determined that the pixel of interest is a color pixel, and the color region signal (_CO
L_DOT) is made "L" active.

As described above, since the halftone dot / color area signal creating unit 32 creates the halftone dot area signal (_AMI) and the color area signal (_COL_DOT), the area discrimination unit 20 determines the color halftone area. Can be determined.

Returning to FIG. 2, the halftone-dot / solid-area-character-region-signal creating unit 33 determines the halftone dot discriminating isolated point signal (WAMI,
KAMI) and solid area signal (_BETA), character area detection edge signal (_EDGL) and character area detection inner edge signal (_INEDG), and halftone dot area signal (_AMI_MOJI) and solid area middle character The area signal (_BETA_MOJI) is created. That is, the halftone-dot / solid-area-character-area-signal creating unit 33 detects a character area existing in the halftone dot or the solid area. As shown in FIG. 14, the OR circuit 75 is provided in the halftone dot / solid area character area signal creating unit 33.
, Three AND circuits 78, 82, 84, an isolated point number counting section 76, an inner edge number counting section 79, and
It includes two comparators 77 and 80 and a continuity detector 81.

Here, the isolated point number counting section 76 is set to 1
The number of isolated points existing in the 1 × 11 matrix area is counted. The inner edge number counting unit 79 is 3
The number of inner edges existing in the × 3 matrix area is counted. Further, the continuity detecting unit 81 detects the continuity of the inner edges, that is, whether or not the inner edges continuously exist.

In this case, the OR circuit 75 is supplied with isolated point signals (WAMI, KAMI) for halftone dot discrimination. Therefore, in the OR circuit 75, "WAMI"
And "KAMI" are calculated. Then, the calculation result is input to the isolated point number counting unit 76. Furthermore, the output from the isolated point number counting unit 76 is
It is input to the terminal P of the comparator 77. On the other hand, the comparator 7
The reference value (CNTREF57-5
0) has been entered.

The AND circuit 78 is also supplied with a character area detecting edge signal (_EDGL) and a character area detecting inner edge signal (_INEDG). For this reason,
In the AND circuit 78, “_EDGL” and “_IN
EDG ”is calculated. Then, the calculation result is input to the inner edge number counting unit 79. Furthermore, the output from the inner edge number counting unit 79 is input to the terminal P of the comparator 80. On the other hand, the reference value (CNTREF67-60) is applied to the terminal Q of the comparator 80.
Has been entered.

The output from the comparator 80 is input to the continuity detector 81. In the continuity detecting unit 81, in the 5 × 5 size matrix data 83 in which the pixel of interest a33 is located at the center, there are three pixels having the same logic as the pixel of interest a33 in any of the eight directions shown in the figure.
The continuity of the inner edge is detected by detecting whether or not the two edges are continuous. Specifically, the continuity of inner edges is detected by the following equation. ! Y = (a11 x a22 x a33) + (a13 x a23 x a33) + (a15 x a24
X a33) + (a35 x a34 x a33) + (a55 x a44 x a33) + (a
53 x a43 x a33) + (a51 x a42 x a33) + (a31 x a32 x a3
3) In the formula, “!” Indicates inversion processing, and “×” indicates AN.
D processing and "+" mean OR processing.

As described above, the continuity detecting unit 81 detects the continuity of the inner edge and considers the detection result, so that it is possible to prevent erroneous determination of image noise or the like as a character area. . That is, the character area can be more accurately determined.

The output from the continuity detector 81 is AN
It is adapted to be inputted to the D circuits 82 and 84, respectively. The output from the comparator 77 is input to the AND circuit 82, and the solid area signal (_BET) is input to the AND circuit 84.
A) is entered. Therefore, the AND circuit 82 outputs the logical product of the output of the continuity detector 81 and the output of the comparator 77 as a halftone dot character area signal (_AMI_MOJI). Further, from the AND circuit 84, the logical product of the output of the continuity detecting unit 81 and the solid area signal (_BETA) is the solid area medium character area signal (_BETA_MOJI).
Is output as.

That is, the halftone dot / solid area character region signal generating section 33 determines that the count value of isolated points is the reference value (CN
TREF57-50), the count value of the inner edge is larger than the reference value (CNTREF67-60), and it is further determined that the inner edge has continuity,
It is determined that the pixel of interest belongs to the halftone dot character area. Also,
The solid area signal (_BETA) is active, and the count value of the inner edge is the reference value (CNTREF67-
60), it is determined that the pixel of interest belongs to the character area in the solid area when it is determined that the inner edge has continuity. Then, the halftone-dot / solid-area-character-area-signal creating unit 33 determines that the pixel of interest belongs to the halftone-dot character area (_AMI_MOJ).
I) is activated, and when it is determined that the pixel of interest belongs to the character area in solid area, the character area signal in solid area (_
BETA_MOJI) is activated.

Returning to FIG. 2 again, the MTF control signal generating section 34 determines the color area signal (_COL_DOT), the halftone dot area signal (_AMI), and the halftone dot character area signal (_AMI_).
MOJI), solid area character area signal (_BETA_M
OJI), internal edge signal for character area detection (_INED)
G), the character edge area signal (_EDG), and the black area signal (_BLACK), the MTF control unit 21.
Control signal (CMPX2-0, K
MPX2-0) is created. The MTF control signal generator 34 is composed of a look-up table, and has seven area discrimination attribute signals (_COL_DOT, _).
AMI, _AMI_MOJI, _BETA_MOJI,
_INEDG, _EDG, _BLACK) is used as an input address to generate an MTF control signal (CMPX, KMPX).

Returning to FIG. 1, the MTF correction unit 21 corrects the sharpness of the image. As shown in FIG. 15, the MTF correction unit 21 includes a cyan (C) correction unit 90, a magenta (M) correction unit 91, and a yellow (Y) correction unit 92 corresponding to each color of CMYK. , And a black (K) correction unit 93, and correction processing is performed for each color. Then, the CMY correction processing is performed by the MTF control signal (CMPX2
-0), and the K correction process is controlled by the MTF control signal (KMPX2-0).

Here, the structure of the correction section for each color will be described in more detail. A cyan (C) correction unit 90, a magenta (M) correction unit 91, and a yellow (Y) correction unit 9
2 and the black (K) correction unit 93 all have the same configuration. Therefore, the configuration of the cyan (C) correction unit 90 will be described here as a representative, and description of the other correction units will be omitted. As shown in FIG. 15, the cyan (C) correction unit 90 includes a matrix creation unit 100, a character processing filter unit 101 including various filters, two selectors 102 and 103, and an adder 1.
04 and are included.

The matrix creating section 100 creates 5 × 5 matrix data and supplies the data to the character processing filter section 101. Character processing filter section 1
01 is an edge enhancement amount creation filter unit 110, a smoothing filter unit 111, and a min filter unit 112.
And a replacement control unit 113. With such a configuration, the character processing filter unit 101 outputs the edge emphasis amount data, the smoothing processing data, the min processing data, and the replacement data.

Here, the edge emphasis amount creation filter unit 11
0 includes a −45 degree differential filter section 120, a 0 degree differential filter section 121, a 45 degree differential filter section 122, and
A 0 degree differential filter unit 123 and a selector 124 for selecting the maximum value of the data filtered by these filter units are included. In this embodiment, the −45 degree differential filter section 120 is provided with the filter shown in FIG. 16, the 0 degree differential filter 121 section is provided with the filter shown in FIG. 17, and the 45 degree differential filter section 122 is provided with the filter shown in FIG. The filter shown in FIG. 18 is provided, and the 90-degree differential filter unit 123 is provided with the filter shown in FIG.

The smoothing filter section 111 is equipped with the filter shown in FIG. 20 so that smoothing processing is executed. Further, in the min filter unit 112, as shown in FIG. 21, a process of setting the minimum value of the 5 × 5 matrix data as the data of the pixel of interest is executed.

As shown in FIG. 22, the replacement control unit 113 includes two AND circuits 114 and 115 and the replacement filter unit 1.
16 and. Then, the AND circuit 114 outputs to the solid area character area signal (_BETA_MOJI).
And a negative logic signal of the character region detection inner edge signal (_INEDG). As a result, the AND circuit 1
In 14, the outer edge area in the solid area character area is detected. On the other hand, the AND circuit 115 is supplied with negative logic signals of the halftone dot character area signal (_AMI_MOJI) and the character area detecting inner edge signal (_INEDG). As a result, the AND circuit 115 detects the outer edge area in the halftone dot character area. And AN
The output signals from the D circuits 114 and 115 are input to the replacement filter unit 116, and the replacement processing is performed here.

The replacement filter section 116 is equipped with the replacement filter shown in FIG. The replacement filter calculates the average value of the brightness of each pixel in the 5 × 5 matrix area centered on the target pixel a33 and replaces the average value with the brightness of the target pixel a33. Therefore, the replacement filter unit 116 replaces the lightness of the outer edge area in the halftone dot character area or the solid area middle character area (hereinafter collectively referred to as “underground character area”).

Here, in the replacement filter section 116,
When a character area is included in the 5 × 5 matrix area, the average value of only the area excluding the character area is calculated. This is because the brightness data to be replaced is made closer to the brightness of the neighboring base region. For example, as shown in FIG. 24, pixels a11, a12, a21, a22, a
If 31, a32, a41, a42, a51, a52 belong to the character area, pixels a13, a14, a1
5, a23, a24, a25, a33, a34, a3
5, a43, a44, a45, a53, a54, a55
The average value calculated by using only the brightness data of is replaced with the brightness data of the target pixel a33.

Returning to FIG. 15, the output from the edge enhancement amount creation filter unit 110 is input to the terminal A of the selector 102. In addition, "0" is applied to the terminal B of the selector 102.
0 "is input to the terminal S, and the MTF control signal (CMPX
2) has been entered. As a result, the selector 102 selects and outputs either the input value to the terminal A or the terminal B according to the content of the MTF control signal (CMPX2).

The output from the smoothing filter unit 111 is input to the terminal A of the selector 103, the output from the min filter unit 112 is input to the terminal B of the selector 103, and the output from the replacement control unit 113 is the selector 10.
3 is input to the terminal E. Furthermore, the selector 103
Outputs from the matrix creation unit 100, that is, data that has not been processed by the character processing filter unit 101 is input to the terminals C and D of the. Then, the MTF control signal (CMPX1-0) is applied to the terminal S of the selector 103.
Has been entered. As a result, in the selector 103,
According to the content of the MTF control signal (CMPX1-0), one of the input values to the terminals A to E is selected and output.

The output from the selector 102 and the output from the selector 103 are input to the terminals A and B of the adder 104, respectively. As a result, the adder 1
In 04, the edge emphasis data (“00” when the edge emphasis is not performed) and the processing data selected by the selector 103 are added, and the addition data is output from the MTF correction unit 21 (C7-0). Becomes For the recording density signals (M, Y, K) of other colors, cyan (C)
Processing similar to is executed.

The image data (C7-0, M7-) of each color processed in the MTF correction unit 21 in this manner.
0, Y7-0, K7-0) is transmitted to an image output device such as a printer via the printer I / F 22. Thus, the reproduced image is output based on the processed image data in the image output device.

Next, the overall operation of the color image processing apparatus having the above configuration will be briefly described. First, the image information of a document is read by the CCD sensor 11.
Then, the analog image data output from the CCD sensor 11 is A / D converted into digital image data. Then, for the digital image data, shading correction, line-to-line correction, chromatic aberration correction,
Magnification / movement processing, color conversion processing, color correction, area discrimination processing,
And MTF correction are sequentially performed. Then, based on the image data that has undergone various types of image processing, the printer I / F 2
A reproduced image of the document is output on the recording medium by a printer or the like via 2.

Here, the area discriminating unit 20 discriminates to which area of the color area, the monochrome area, the halftone dot area, the character area, and the underlying character area the pixel of interest belongs. For the halftone dot area, the character area, and the halftone dot character area, it is also determined whether those areas are color areas. Then, the determination of the color halftone dot area is
This is performed based on the result of discrimination between the halftone dot area and the color area in the halftone dot / color area signal creating unit 32. So first,
A method of discriminating a halftone dot area will be described.

To determine the halftone dot area, first, in the black isolated point number counting section 60 and the white isolated point number counting section 61, the halftone dot determining isolated point signals (WAMI and KAMI) created by the various signal creating sections 31 are generated. Based on 9x4
The number of black isolated points and white isolated points present in each of the five matrices is counted. Then, by the adder 63,
An added value of the count values of the black isolated point and the white isolated point is calculated. Then, in the comparators 64 to 66, the added value of the count values of the black isolated point and the white isolated point, the count value of the black isolated point, and the count value of the white isolated point are used as the reference values (CNTREF17-).
10, 27-20, 37-30). The comparison result in each of the comparators 64 to 66 is the OR circuit 68.
Entered in.

In the OR circuit 68, when the total value of the number of black isolated points and the number of white isolated points is larger than the reference value (CNTREF17-10), the number of black isolated points is the reference value (CNTREF27-20). )
If the number of white isolated points is greater than the reference value (CNTREF37-30) and at least one of the conditions is satisfied, it is determined that the pixel of interest belongs to the halftone dot area. Then, the halftone dot area signal (_AMI) is made "L" active.

Next, a method of discriminating the color area will be described. To determine the color region, first, the color pixel number counting unit 62 counts the number of color pixels existing in the 9 × 45 matrix based on the color signal (COLOR) created by the color signal creating unit 30. Then, the comparator 67 compares the count value of the color pixel with the reference value (CNTREF47-40). As a result, the reference value of the number of color pixels (CNTREF47
-40), it is determined that the pixel of interest belongs to the color area. Then, the color area signal (_
COL_DOT) is made "L" active. In this way, as a result of the discrimination between the halftone dot area and the color area in the halftone dot / color area signal creating unit 32, both the halftone dot area signal (_AMI) and the color area signal (_COL_DOT) are "L" active. Area determination unit 2
At 0, the pixel of interest is determined to belong to the color halftone dot area.

Next, a method of discriminating the character area in the background will be described. The determination of the character area in the background is performed by the halftone dot / character area in the background area signal generation unit 33 provided in the area determination unit 20.
In the above, the process is divided into the determination of the halftone dot character region and the determination of the solid region character region. First, the determination of the halftone dot character area will be described. To determine a character area in a halftone dot, first, in the OR circuit 75, the halftone dot discriminating isolated point signal (WAMI, KAM) generated by the various signal generating unit 31 is used.
The logical sum of I) is calculated. Then, the logical sum calculated by the OR circuit 75 is input to the isolated point number counting unit 76. Then, the isolated point number counting unit 76 counts the number of white and black isolated points existing in the 11 × 11 matrix area. Then, in the comparator 77, the isolated point count value is changed to the reference value (CNTREF
57-50). The comparison result is input to the AND circuit 82.

On the other hand, in parallel with the above processing, the AND circuit 7
In 8, the logical product of the character area detection edge signal (_EDGL) created by the various signal creation unit 31 and the character area detection inner edge signal (_INEDG) is calculated. Then, the logical product calculated by the AND circuit 78 is input to the inner edge number counting unit 79. Then, the inner edge number counting unit 79 counts the number of inner edges existing in the 3 × 3 matrix area. Then, in the comparator 80, the inner edge count value is compared with the reference value (CNTREF67-60). The comparison result is input to the continuity detecting unit 81. Then, the continuity detector 81 detects the continuity of the inner edge. Then, the count value of the inner edge and the data regarding the presence / absence of continuity are input to the AND circuit 82.

Finally, in the AND circuit 82, the isolated point count value (WAMI + KAMI) is equal to the reference value (CN
TREF57-50), the inner edge count value (_EDGL × _INEDG) is larger than the reference value (CNTREF67-60), and the inner edge has continuity, the pixel of interest is a halftone dot character. It is determined that the character area signal (_AMI)
_MOJI) is made "L" active. In order to determine the character area in the halftone dot, the pixel of interest is moved by one pixel in the main scanning direction, and when it reaches the final position in the main scanning direction, it is moved by one pixel in the sub scanning direction. It is performed for all the pixels of the image data.

Next, the determination of the character area in the solid area will be described. The data regarding the presence / absence of continuity of the inner edge output from the continuity detecting unit 81 is the AND circuit 84.
Is also entered. Further, the AND circuit 84 outputs the solid area signal (_BET) output from the solid area signal creating unit 26.
A_MOJI) has been input. When the AND circuit 84 belongs to the solid area and the inner edge has continuity, it is determined that the pixel of interest belongs to the solid area character area, and the solid area character area signal (_BETA_M
OJI) is made "L" active. Note that in the determination of the character area in the solid area, the pixel of interest is moved by one pixel in the main scanning direction, and when it reaches the final position in the main scanning direction, it is moved by one pixel in the sub scanning direction. It is performed for all the pixels of the image data.

Then, according to the result of the area discrimination performed by the area discriminating unit 20, that is, according to various area attribute discrimination signals
The MTF correction unit 21 performs image processing according to various attributes. Specifically, the smoothing process is performed on the base region. Further, the edge enhancement processing is applied to the inner edge area of the character area, and the edge attenuation processing is applied to the outer edge area. Thereby, the generation of moire is suppressed in the base region, and the sharpness is secured in the character region.

Edge enhancement processing is applied to the inner edge area in the character area in the background area. On the other hand, the replacement filter unit 116 performs the replacement process on the outer edge area in the character area in the background area. For example, in FIG.
If the image is as shown in FIG. 5, the area R outside the character area
Is the target of the replacement process. Then, the pixels belonging to the region R are subjected to the lightness replacement processing by the replacement filter. That is, the average brightness of the background region in the replacement filter is replaced with the brightness of the pixel of interest located at the center of the replacement filter. As a result, the brightness of the region R becomes substantially equal to the brightness of the base region. Therefore, FIG.
As shown in, the white border (see FIG. 28) does not occur around the characters drawn in the base region. In addition, since the area R is not subjected to the smoothing process, color turbidity does not occur. That is, by the correction of the MTF correction unit 21, an image such as a character drawn on the background can be reproduced without causing white edging or color turbidity and without lowering the sharpness.

Here, in the above description, the case where the image processing apparatus according to the present invention is configured by hardware has been exemplified, but such an apparatus can also be realized by software. Therefore, the flow of processing in the case where the above image processing apparatus is realized by software will be described using the flowchart shown in FIG.

First, the software is read by a computer (for example, a copying machine or a printer). When the reading is completed, the computer and the software of the present invention cooperate to execute the following processing. That is, the computer first waits for the input of image data (# 11). Then, when the image data is input (# 11: YES), the computer creates lightness data for each pixel (# 1).
2). When the brightness data is created, the computer discriminates the pixels belonging to the edge area based on the brightness data (# 13). Then, the process of # 15 is executed for the pixels determined to belong to the edge area (# 14: YE).
S). On the other hand, other processing (specifically, smoothing processing) is performed on the pixels determined not to belong to the edge area.
(# 14: NO, # 22).

Next, at # 15, the computer
It is determined whether the pixel determined to belong to the edge region belongs to the inner edge region or the outer edge region. Subsequently, the computer determines whether the pixel determined to belong to the edge area also belongs to the base area (# 16). When it is determined that the pixel determined to belong to the edge area belongs to the outer edge area (# 1
7: YES), # 18 is executed. On the other hand, when the pixel determined to belong to the edge area does not belong to the outer edge area, in other words, the pixel belongs to the inner edge area (# 17: NO), other processing (specifically, for that pixel) is performed. Edge enhancement processing) (# 22). The “other processing” of # 22 includes a plurality of processings such as smoothing processing and edge enhancement processing as described above.

Further, when the computer determines that the pixel which is determined to belong to the outer edge area also belongs to the background area (# 18: YES), the average density in the background area around the pixel is calculated. (# 19). Then, when the computer calculates the average density, it replaces the calculated average density with the density of the pixel (# 20). On the other hand, when it is determined that the pixel determined to belong to the outer edge area does not belong to the base area (# 18: NO), edge attenuation processing is performed on the pixel (# 21).

By loading the software that performs the processing of such a procedure into an image processing apparatus (corresponding to a computer) in which the above hardware is not configured, the same effect as that of the above image processing apparatus can be obtained. .
That is, it is possible to clearly reproduce the characters on the background without causing white edging or color turbidity. The software may exist as a program or a recording medium recording the program.

As described above in detail, according to the color image processing apparatus according to the present embodiment, the area discrimination unit 20
In addition, an edge signal generation unit 25 that detects an edge area and determines whether the edge area is an inner edge area or an outer edge area, and a halftone dot or a halftone dot area that detects a character area in a background area of a predetermined density. A dot / solid area character area signal creation unit 33 is provided. As a result, the inner edge area and the outer edge area of the character area formed on the base area can be accurately distinguished. Then, the MTF correction unit 2
1 is provided with a replacement control unit 113 that performs a brightness replacement process on the outer edge region of the character region formed on the base region. Therefore, a white border does not occur around the character formed on the base region. Further, the outer edge area of the character area is not subjected to the replacement processing and the smoothing processing by the replacement control unit 113, so that the characters formed on the background area may have color turbidity. Absent.

The above-described embodiment is merely an example, does not limit the present invention, and it is needless to say that various improvements and modifications can be made without departing from the scope of the invention. Further, it goes without saying that the specific numerical values (for example, the size of the logical filter) exemplified in the above-mentioned embodiments are merely examples.

[0091]

As described above, according to the present invention, an image processing apparatus and an image processing program capable of clearly reproducing a character or the like formed on a base region without causing white edging or color turbidity. Is provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a color image processing apparatus according to an embodiment.

FIG. 2 is a block diagram showing a schematic configuration of a region discriminating unit in FIG.

FIG. 3 is a block diagram showing a schematic configuration of a color signal generation unit in FIG.

FIG. 4 is a block diagram showing a schematic configuration of an edge signal generation unit in FIG.

FIG. 5 is a diagram showing a first-order differential filter (main scanning direction).

FIG. 6 is a diagram showing a first-order differential filter (sub-scanning direction).

FIG. 7 is a diagram showing a second-order differential filter (+ type).

FIG. 8 is a diagram showing a second derivative filter (× type).

FIG. 9 is a diagram showing an outer / inner edge discrimination filter.

FIG. 10 is a diagram showing an isolated point detection filter.

FIG. 11 is a diagram for explaining a determination method in an outer / inner edge determination unit in FIG.

FIG. 12 is a flowchart showing processing contents in a solid area signal creation unit in FIG.

FIG. 13 is a block diagram showing a schematic configuration of a halftone / color area signal generation unit in FIG.

FIG. 14 is a block diagram showing a schematic configuration of a halftone dot / solid area character area signal generating unit in FIG. 2;

15 is a block diagram showing a schematic configuration of an MTF correction unit in FIG.

FIG. 16 is a diagram showing a −45 degree differential filter.

FIG. 17 is a diagram showing a 0-degree differential filter.

FIG. 18 is a diagram showing a 45-degree differential filter.

FIG. 19 is a diagram showing a 90-degree differential filter.

FIG. 20 is a diagram showing a smoothing filter.

FIG. 21 is a diagram showing a min filter.

22 is a block diagram showing a schematic configuration of a replacement control unit of FIG.

FIG. 23 is a diagram showing a replacement filter.

FIG. 24 is a diagram for explaining a processing method by a replacement filter.

FIG. 25 is a diagram showing a specific example of a processed image.

FIG. 26 is a diagram showing a processing result for the image of FIG. 25.

FIG. 27 is a flowchart showing the processing contents when the present invention is realized by software.

FIG. 28 is a diagram for explaining a problem in the conventional technique.

[Explanation of symbols]

11 CCD sensor 20 Area discriminator 21 MTF correction unit 25 Edge signal generator 26 Solid Area Signal Creation Unit 32 halftone dot / color area signal creation unit 33 halftone dot / solid area character area signal creation unit 49 Outer / inner edge determination unit 113 Replacement control unit 102,103 selector

Continued front page    F-term (reference) 2C062 AA37                 5B057 AA11 BA02 BA30 CA01 CA08                       CA12 CA16 CB01 CB08 CB12                       CB16 CC03 CE05 CE06 CE11                       CE17 CH09 DA08 DB02 DB06                       DB09 DC16 DC25                 5C077 LL08 LL09 MP02 MP05 PP03                       PP27 PP28 PP46 PP68 PQ12                       TT06                 5L096 AA02 AA06 FA06 FA43 FA44                       GA04 GA55

Claims (6)

[Claims] 1. An image data acquisition unit that acquires image data, and determines whether or not a pixel of interest belongs to an outer edge region, which is an outer portion of the edge region, based on the image data acquired by the image data acquisition unit. An outer edge discriminating means, a base area discriminating means for discriminating whether or not the pixel of interest belongs to the base area based on the image data acquired by the image data acquiring means, and the outer edge discriminating means. For the target pixel determined to belong to the outer edge region by the first correction unit, and for the target pixel determined to belong to the outer edge region by the outer edge determination unit A second correction unit that performs a second correction process different from the first correction process, and a pixel of interest determined to belong to an outer edge region by the outer edge determination unit, For the pixel of interest that is determined not to belong to the background area by the background area determination means, the first correction means first
Correction processing determining means that determines to perform the second correction processing by the second correcting means on the pixel of interest that is determined to be performed by the background area determining means and that belongs to the background area. An image processing apparatus comprising: 2. The image processing device according to claim 1, wherein the first correction processing by the first correction means is edge attenuation processing, and the second correction processing by the second correction means is a target pixel. The image processing apparatus is characterized in that it is a replacement process for replacing the density of the image with the peripheral density thereof. 3. The image processing apparatus according to claim 2, wherein the replacement process is a process of replacing with an average density of a region detected as a background region by the background region determination means. Image processing device. 4. An image data acquisition unit that acquires image data, and determines whether the pixel of interest belongs to an outer edge region that is an outer portion of the edge region based on the image data acquired by the image data acquisition unit. An outer edge discriminating means, a base area discriminating means for discriminating whether or not the pixel of interest belongs to the base area based on the image data acquired by the image data acquiring means, and the outer edge discriminating means. Replaces the density of the pixel of interest that is determined to belong to the outer edge area and that is determined to belong to the background area by the background area determination means to a value calculated based on the density of the peripheral pixels of the pixel of interest. An image processing apparatus, comprising: 5. The image processing apparatus according to claim 4, wherein the replacement unit is a region that is determined to be a background region by the background region determination unit as a value calculated based on the densities of peripheral pixels of the pixel of interest. An image processing apparatus characterized by using the average density in. 6. An image data acquisition step of acquiring image data in a computer, and whether or not the pixel of interest belongs to an outer edge area which is an outer portion of the edge area based on the image data acquired in the image data acquisition step. An outer edge determination step of determining the background area, a background area determination step of detecting a background area by determining whether or not the pixel of interest belongs to the background area based on the image data acquired in the image data acquisition step, Among the target pixels determined to belong to the outer edge area in the edge determination step, with respect to the target pixel determined to belong to the base area in the base area determination step,
An image processing program for executing a replacement process step of performing a replacement process for replacing the density of the pixel of interest with the average density in the area detected as the background area in the background area determination step.